Demonstration of Ground Vehicle Navigation with Non-Cooperative Multi-Constellation LEO Satellites

An experimental demonstration of a ground vehicle navigating exclusively with non-cooperative multi-constellation low Earth orbit (LEO) satellite signals of opportunity is presented. The satellites’ unknown downlink signals are processed through a cognitive software-defined receiver to extract Doppler frequency measurements. To account for the satellites’ uncertain timing and ephemerides, a correction approach is employed in a standalone fashion (i.e., by the vehicle-mounted receiver) during an initial period of global navigation satellite system (GNSS) signal availability. The approach accounts for ephemerides reference time errors and large orbit errors that are inherited from simplified general perturbation 4 (SGP4) open-loop propagation of publicly available two-line element (TLE) files. Results are presented showcasing the ground vehicle navigating by fusing via an extended Kalman filter (EKF) Doppler measurements from 4 Starlink, 1 OneWeb, 2 Orbcomm, and 1 Iridium NEXT LEO satellites. The vehicle traversed a total trajectory of 1.58 km in 70 seconds, during which GNSS signals were unavailable for the final 1.054 km, corresponding to a 40-second duration. Without GNSS, the unaided navigation solution resulted in a three-dimensional (3D) root mean squared error (RMSE) of 110 m. In contrast, navigating with LEO signals of opportunity achieved an RMSE of 4.15 m, which is an unprecedented level of accuracy with non-cooperative LEO.